Lazy-loading :
Lazy loading (also known as asynchronous loading) is a design pattern commonly used in computer programming to defer initialization of an object until the point at which it is needed. It can contribute to efficiency in the program's operation if properly and appropriately used. This makes it ideal in use cases where network content is accessed and initialization times are to be kept at a minimum, such as in the case of web pages. The opposite of lazy loading is eager loading.
Bydefault lazy loading is true.Lazy loading means when the select query is executed it will not hit the database. It will wait for getter function i.e when we required then ,it will fetch from the datbase. for example: You are a parent who has a kid with a lot of toys. But the current issue is whenever you call him (we assume you have a boy), he comes to you with all his toys as well. Now this is an issue since you do not want him carrying around his toys all the time. So being the rationale parent, you go right ahead and define the toys of the child as LAZY. Now whenever you call him, he just comes to you without his toys.
Say you have a parent and that parent has a collection of children. Hibernate now can "lazy-load" the children, which means that it does not actually load all the children when loading the parent. Instead, it loads them when requested to do so. You can either request this explicitly or, and this is far more common, hibernate will load them automatically when you try to access a child.
Lazy-loading can help improve the performance significantly since often you won't need the children and so they will not be loaded.
Also beware of the n+1-problem. Hibernate will not actually load all children when you access the collection. Instead, it will load each child individually. When iterating over the collection, this causes a query for every child. In order to avoid this, you can trick hibernate into loading all children simultaneously, e.g. by calling parent.getChildren().size().
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